1. The Field of the Invention
This invention relates to a method for preparing homo- and co-polymers of cyclic olefin compounds. More particularly, this invention relates to a method for preparing homo- and co-polymers by polymerization of cyclic olefin compounds that uses an organic boron compound as a catalyst activator, forming a homogeneous catalyst system having a high solubility in a non-polar solvent, together with a nickel salt compound and an organoaluminoxane compound to prepare cyclic polymers having high molecular weights in high yields.
2. Related Prior Art
The copolymer of ethylene or propylene and a cyclic olefin compound is endowed with excellent properties such as transparency, heat resistance, etc., which hardly appear in the existing polymers such as polyethylene or polypropylene, with the introduction of a rigid ring structure such as norbornene into the main chain of the polymer. Accordingly, the homopolymer/copolymer of a cyclic olefin compound is expected to substitute for a polycarbonate (PC) or polymethylmethacrylate (PMMA) resin currently used as an information recording material, and possibly utilized as an optical material with transparency and low moisture absorption for various applications such as DVD, CD, lens, optical fiber, and the like.
Currently, various norbornene derivatives having different alkyl groups and polar functional groups are used for the preparation of cyclic olefin polymers. Such norbornene derivatives are useful for the preparation of homopolymers as well as copolymers using ethylene or propylene.
Some advanced manufacturers of cyclic olefin polymers have recently been developing novel materials having epoch-making thermal, mechanical and optical properties, which are unattainable by the existing polyolefins, through copolymerization of styrene, cyclic olefin, methylmethacrylate, or the like. In particular, the polymers prepared by copolymerization of cyclic olefin and ethylene are standing in the spotlight as a next-generation information recording material such as CD, DVD, and so forth due to their remarkably excellent optical and thermal properties.
The norbornene polymers not only substitute for polycarbonate used for the aforementioned applications but also reduce the space between CD tracks to allow high integration, so they are applicable to next-generation DVD (e.g., HD-DVD), or the like. In addition, such norbornene polymers are widely used for more various applications such as camcorders or automobile cameras due to their excellent properties such as optical properties, dimensional stability, excess moisture tolerance, low density, and so forth.
The polymerization catalysts for preparation of a polymer using a cyclic olefin compound can be classified into an addition polymerization catalyst, a ROMP (Ring Opening Metathesis Polymerization) catalyst, and a cationic catalyst, including a radical initiator.
Among these, the addition polymerization catalyst, the ROMP catalyst and the cationic catalyst have a common characteristic that they can be used for preparation of cyclic olefin polymers with high transparency. The use of the ROMP catalyst necessarily demands a step of saturating the double bonds of the polymer after polymerization, and the addition polymerization catalyst is used for preparation of a cyclic olefin polymer having a low dielectric property (i.e., insulating property).
The representative metals constituting the addition polymerization catalyst include Ti, Zr, Cr, Co, Ni, Pd, and the like. Among these metals, Ni and Pd are representative metals for preparation of a cyclic olefin polymer.
The representative main metals constituting the ROMP catalyst include Mo, W, Ru, Re, or the like. The activity of the catalyst can be controlled through a modification of the ligands around the metal or a change in the additives.
The cyclic olefin polymer, whose principal advantages are low density, high transparency, low moisture absorbency, and heat resistance, is expected to substitute for glass, acrylic polymer, polycarbonate, and polyvinylidene chloride (PVDC).
As an example of the conventional methods using a transition metal as a polymerization catalyst in the preparation of homo- and co-polymers from norbornene and its derivatives, U.S. Pat. No. 3,330,815 discloses a method for addition polymerization of norbornene using a complex prepared from TiCl3 (or TiCl4) and an organoaluminum compound, or Pd(C6H5CN)2Cl2 as a catalyst. Disadvantageously, this method provides a polymer having a number average molecular weight (Mn) of less than 10,000 in a low yield.
Another example is a method for addition polymerization of norbornene and its derivatives using a complex prepared from a bidentate ligand, Ni(0) salt and B(C6F5)3 as disclosed in U.S. Pat. Nos. 6,350,837 B1 and 6,538,085 B2. In this case, however, one of the components of the catalyst, B(C6F5)3 is a very expensive compound, so the method is limited in its industrial uses.
U.S. Pat. No. 5,705,503 discloses a method for addition polymerization of a norbornene derivative using a Zwitterion complex prepared from palladium metal. However, this method requires an excess amount of the catalyst with respect to the amount of the monomer (the molar ratio of monomer to catalyst is less than 250) and a polymerization time of 12 hours or more for a relatively high yield. A similar method is disclosed in U.S. Pat. Nos. 6,262,194B1 and 6,265,506B1, which relates to a method for addition polymerization of norbornene using a Zwitterion complex prepared from palladium metal. This method is also disadvantageous in that the complex should be prepared by coordination of ligands of a specific structure with palladium metal, which makes it difficult to apply the method to industrial large-scaled production of the polymer.
European Patent Application No. 0 504 418A1 (filed on Sep. 23, 1992) discloses a method for addition polymerization of a cyclic olefin compound in the presence of A) a transition metal salt compound, B) a compound capable of forming an ionic complex with the compound A), and C) an organoaluminum compound.
Other examples of the cyclic olefin polymerization method using a transition metal as a catalyst include a cyclic olefin polymerization method using a Zirconocene compound and an aluminoxane compound (Japanese Patent Application Laid-open Kokai No. Sho 64-66216), and a method for copolymerization of norbornene and an olefin compound using a transition metal salt compound and an aluminoxane compound (Japanese Patent Laid-open Nos. 61-221206 and 64-106). However, these methods require an excess amount of the aluminoxane compound, causing discoloration of the product, and requiring a step of removing catalyst residues in the polymer after the polymerization reaction, thus reducing productivity.
Japanese Patent Laid Open Nos. 61-271308 and 62-252406 disclose methods for copolymerization of norbornene and olefin using a catalyst system comprising a vanadium compound and an organoaluminum compound, which methods involve an extremely low catalyst activity.
The methods for addition polymerization of a cyclic olefin compound using a metallocene catalyst are disclosed in U.S. Pat. Nos. 5,087,677 and 5,371,158, which are directed to a method for homo- and co-polymerizations of norbornene derivatives using a Ti-, Zr-, Hf-, V-, Nb- or Ta-based metallocene complex as a main catalyst and an aluminoxane compound as a cocatalyst. However, these methods mostly provide a low polymerization yield of less than 50%.
In addition, U.S. Pat. No. 5,621,054 discloses a method for copolymerization of norbornene and ethylene using a catalyst activator, N,N-dimethylanilinium tetrakis-perfluorophenylboron and a metallocene catalyst prepared by coordinating ligands of a unique structure to a metal such as Hf or Zr without an organoaluminum or aluminoxane compound. Disadvantageously, the method also has the difficulty in application to commercialized processes because of the extremely unique structures of the ligands and the catalyst activator.
In addition to the aforementioned problems, the above-described conventional techniques have the difficulty in forming a homogeneous catalyst system having a high solubility in a non-polar solvent and in preparing a cyclic olefin polymer having a high molecular weight in a high yield.
Compared with a solution polymerization using a homogeneous catalyst system having a high solubility in a non-polar solvent, a solution polymerization using a heterogeneous catalyst system forming a suspended solid due to incomplete dissolution in a non-polar solvent is ready to cause gel formation, so the gel thus produced greatly increases the solution viscosity of the polymer and accumulates on the wall of the reactor or the pipe line to inhibit the flow of reactants or products.
Namely, the heterogeneous catalyst system with poor solubility has a difficulty in quantitative control of the catalyst essential to the uniform progress of the reaction and the property control of the product, relative to the homogeneous catalyst system excellent in solubility.